So, it’s a bug with Mei, but technically I ts a bug for heroes that have targeted abilities when interacting with a Mei.
My best example of this is an interaction with Mei and Mercy. If Mei goes in her ice block, Mercy can no longer Guardian Angel to her, and her beams will break after entering ice block after the normal 1 second duration if Mercy’s beams lost line of sight, despite Mei being perfectly visible.
Ana has a similar thing with Nano Boost, and Echo can’t duplicate enemy Mei’s in cryo either.
This really needs looking into. It’s really annoying trying to save/duplicate a Mei just for her to die/not being able to clone her until cryo ends.